In the manufacture of glass fiber mats, many blends and mixtures involving urea-formaldehyde resins have been used as binders to fix glass fibers and lend strength in the mat product. One such blend comprises a mixture of urea-formaldehyde resin with a mixture of styrene-butadiene latex and an acrylamide as described in U.S. Pat. No. 4,258,098. While this binder blend provides mats of high tensile strength, their flexibility at mandrel diameters (MD) of 100 mm or less fail to meet specifications. Specifically at MD 100 mm or less, the mat is subject to cracking and crumbling which is a serious falling in applications where the mat is employed as a base in asphalt roofing shingles, as a backing felt or as a base support for sheet vinyl flooring. Additionally, it is found that certain acrylamides are incompatible with dispersion aids employed in the formation of glass fiber slurries preliminary to matting. These are generally subject to gelation and cause plugging of process lines and pumping difficulties.
It has also been noted that the binder composition of the above patent lacks the desired wettability for commercial applications where a web of mat fiber is conveyed past the point of binder application at high speeds allowing less than 10 seconds for wettability. In such operations the binder is unevenly deposited on the surface of the mat causing objectionable non-uniform mat strength and porosity. Finally, the low pH, less than 5, of these latexes causes premature reaction leading to cross-linking, phase separation and gelation which contribute to binder voids in the mat and non-uniform binder distribution resulting in poor mat strength.
Accordingly it is an object of this invention to provide a binder for glass fiber mats which has greatly improved flexibility and wettability and which is compatible with known dispersion aids.
Another object of this invention is to provide a binder having the above properties with enhanced mat tensile strength.
Another object is to provide a binder composition which is readily incorporated and uniformly distributed on the surface of a glass fiber mat and which is ideally suited for use as a backing felt or base support in roofing or flooring.
Still another object of this invention is to provide a simplified process for binding glass fibers in a mat which is commercially feasible and which requires less care in formulating.
These and other objects of the invention will become apparent to those skilled in the art from the following description and disclosure.